README ¶ 二叉树的层序遍历 II 给你二叉树的根节点 root ,返回其节点值 自底向上的层序遍历 。 (即按从叶子节点所在层到根节点所在的层,逐层从左向右遍历) 示例 1: ``` 输入:root = [3,9,20,null,null,15,7] 输出:[[15,7],[9,20],[3]] **示例 2:** 输入:root = [1] 输出:[[1]] **示例 3:** 输入:root = [] 输出:[] **提示:** * 树中节点数目在范围 `[0, 2000]` 内 * `-1000 <= Node.val <= 1000` Expand ▾ Collapse ▴ Documentation ¶ There is no documentation for this package. Source Files ¶ View all Source files binary-tree-level-order-traversal-ii.go Click to show internal directories. Click to hide internal directories.